In a cellular radiotelephone network, such as the GSM network, the mobile telephones transmit to the base stations at a power level which depends on the construction characteristics of each type of telephone and which are defined by a power class.
This class is stored in the telephone and, when it is energised, it announces itself to the network by automatically transmitting this class and various data indicating its characteristics and its functions. When communication is established, the network controls the level of transmission of the telephone according to this class, ie. in the case of low reception at the base station linked to the telephone, the network will attempt to remotely control an increase in the transmission level of the telephone only if the maximum transmission level associated with its class has not already been reached. Otherwise the network will simply attempt to correct the errors in reception.
As long as the maximum level has not been reached the network remotely controls the level of transmission of the telephone so that this will be just sufficient to avoid errors, this avoids wasting the telephone""s power and is thus advantageous to its autonomy.
The radio transmission represents a large part of the telephone""s consumption, it having very limited autonomy in the power supply, batteries or cells, storing electrical power. In the case of severe discharging, the power supply is incapable of supplying the desired current and must be changed or recharged.
The present invention aims to prolong the xe2x80x9clifespanxe2x80x9d of such a power supply, ie. to increase the quantity of useful power that it is possible to extract therefrom between two recharges, if this is the case.
To this end, the invention relates to a process for controlling the power supply of a telephone of a cellular radiotelephone network, of which the transmission power is controlled by the network according to a nominal power class indicted by the telephone, characterised in that
the charge level of the power supply is determined,
the maximum transmission power able to be reached is deduced from the charge level,
the maximum transmission power and the transmission power controlled by the network are compared, and
the mobile telephone is downgraded if the former is lower than the latter.
Thus, when the power supply becomes incapable of providing the desired power it is possible to proceed with the extraction of power therefrom in a downgraded mode of operation which requires less power.
The telephone is advantageously downgraded into a fictitious class of transmission power lower than that of the nominal class.
It is thus possible to return to standard operation with automatic power control but in a lower range of transmission power levels.
In this case any connection between the telephone and the network is preferably cut in order then to reestablish such a connection and to transmit the indication relative to the fictitious class.
The switching between classes thus does not risk disrupting the network since this network cannot establish a logic link between the telephone which has xe2x80x9cdisappearedxe2x80x9d and the same telephone reappearing with immediately reduced power.